I live by the approach that you give the amount of fuel the smoker wants. Truth is it might not be the same every time because of uncontrollable variables such as the weather, baro, wind, humidity, etc... This is the beauty of a offset smoker. The guys who do not want to wrangle fire management buy pellets,gas grills,etc......
You have a nice smoker so the amount of fuel should be in the same ballpark, but don't worry if you may need more/less fuel each cook for your desired temp range. It might be different.
You will find that many here don't use "store" charcoal, I did years ago, now I just use all wood and as Smitty stated use the older hot wood(red coal) as a bed of coals for the new splits that I add throughout the cook. I never warm splits or pre heat them. I just dont overlaod the firebox with fuel.
I try to control my temp by the amount of wood vs just intake or exhaust. I leave the exhaust and intake open usually. I find the more wood I add, the more I have to leave the door open or intake. So I start slow and add wood as needed. Its a balancing act that you learn. Sounds like you had more fuel than you needed at that time.
You will have to just learn what your smoker likes.